The present invention relates to a method and apparatus for post forming laminate tops. Post formed tops are made by adhering a sheet of laminate material to a top substrate, either wood or metal and forming a suitable edge thereon. The laminate may be either a thermosetting material or a thermoplastic material such as vinyl. The most commonly used laminate employs a melamine overlay on a thermolinking phenolic substrate. This is the most readily available laminate and is intended for use with both metal and wooden top substrates.
The basic first step in any post forming operation is adhering the laminate to the top substrate. A portion of the laminate overhangs the periphery of the substrate and must be formed downwardly over the periphery of the substrate. In the past, the most critical problem encountered in this operation is that of the overhanging laminate cracking as it is formed over the periphery of the substrate. It has proven particularly difficult to perform this operation where the top substrate is made of metal. Further, there are severe limitations on how tight a radius the laminate can be formed over. Typically, prior artisans have been able to form laminates only to a 5/8 inch radius. Also, it has been necessary for prior artisans to use thinner laminates in order to minimize cracking, i.e. laminates of approximately 0.030 inches.
Prior art methods typically teach heating only the top surface of the laminate, perhaps to avoid overheating and blistering. Also, prior art methods teach heating the overhanging laminate portion relatively slowly, again apparently in order to avoid blistering of the laminate. It has been generally accepted in the industry to employ some type of heat source, radiant or contact, at approximately 350.degree. F. for a period of roughly 35 to 45 seconds. Most manufacturers then relatively slowly fold the overhanging laminate over the periphery of the substrate. Some attempt to do this more quickly, but their complicated mechanisms typically cannot form very rapidly.
Prior art forming devices themselves often create problems. This is particularly true when the laminate must not only be formed over the upper edge of the substrate, but also over its lower edge. One mechanism for achieving this uses two separate former bars and two separate drive mechanisms for them. The first former bar is used to make the first corner and a second former bar is used to make the second corner. However these mechanisms are cumbersome and have not contributed significantly to the solution of the laminate cracking problem.
One prior art technique which has been devised to minimize cracking involves taping the top surface of the overhanging laminate portion prior to heating. Some may also tape the bottom surface. The overhanging portion is then heated and formed. The tape is supposed to minimize laminate cracking. One very significant problem with the method, however, is that the tape must be peeled off of the exposed surface of the laminate after it has been formed. This is a costly and messy operation.
Accordingly, there has been a significant need for a method and apparatus for post forming laminate tops which will be capable of commercial operation with only a minimum of scrap as a result of cracked laminate surfaces.